Motor operated valves normally contain a spring pack which is biased whenever torque is applied to the valve shaft. A torque switch is coupled to the spring pack such that when a certain level of torque is reached, such as at the fully open or fully closed position of the valve shaft, the switch stops the motor and prevents it from applying any more torque.
As can be imagined, should the spring pack not conform to specifications by generating false or inaccurate measurements, the torque switch will be inappropriately triggered. If the switch is triggered too early, the valve may not be in its fully open or fully closed position thereby affecting flow through the valve. If the switch is triggered too late, the motor will be allowed to operate too long thereby possibly causing damage to the valve body or stem. Thus it is important for spring packs to accurately operate within their specified range.
In the past, two separate steps were required to test the spring packs for motor operated valves. The first step involved the compressing of the spring pack in a test stand. Generally, the test stand utilized a load cell and a LDT sensor that fed into a display box. At various times during the test, different compression readings were manually taken. The second step involved entering this recorded data into a computer so that a software program could graphically display the entered data. Afterwards, this data was evaluated and, depending upon the evaluation, the spring pack was either re-inserted into the motor operated valve or it was discarded, there were no provisions for comparing the data just entered with any previous test data or standard.
It is thus an object of this invention to provide a method and apparatus for testing spring packs which is quicker, more accurate, and more efficient than any such system now known. Another object of this invention is to provide a system that automatically feeds (if such is desired) certain test data to a computer for analysis. Other embodiments permit the user to semi-automatically feed such data to the computer or this data can be manually entered. Still another object of this invention is to provide a spring pack test stand that is easy to use without the need to bolt or otherwise fasten the spring pack to the test stand. These and other objects will become obvious upon further investigation.